(1)Select grenade
(2) Press left mouse button once to pull pin.
(3) Press left mouse button and HOLD it down either till it's auto thrown, or a short time to throw at a
target in close.
Sounds like you are pressing the button once and only pulling the fuse pin. The fuse timmer runs out and it kills you.
And I have a question to anyone about the sound in the demo (don't own the full game), and that is, have you noticed if you turn the sound up high that it hisses a lot? Maybe I need something other than the onboard 2-channel nForce2 sound if it does'nt.